Question

In the modern periodic table, magnesium is surrounded by elements with atomic numbers 4, 11, 13, and 20. Identify the elements. Which of these have chemical properties resembling magnesium?

Answer 1

To solve this question, we need to determine the electronic configurations of magnesium and the elements with atomic numbers 4, 11, 13, and 20. The atomic number of magnesium is 12.

Complete answer:
The atomic number of magnesium (Mg) is 12. The electronic configuration of magnesium (Mg) is
$_{12}Mg=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}$
Now, the element having atomic number 4 is Beryllium (Be). The electronic configuration of Beryllium (Be) is
$_{4}Be=1{{s}^{2}}2{{s}^{2}}$
The element having atomic number 11 is Sodium (Na). The electronic configuration of Sodium (Na) is
$_{11}Na=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{1}}$
The element having atomic number 13 is Aluminum (Al). The electronic configuration of Aluminum (Al) is
$_{13}Al=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{1}}$
The element having atomic number 20 is Calcium (Ca). The electronic configuration of Calcium (20) is
$_{20}Ca=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}4{{s}^{2}}$
Now, we know that in the modern periodic table, "the element's physical and chemical properties are the periodic function of their atomic masses."
So, the elements which are present in the same group have the same number of electrons in their outermost shell and hence have similar chemical and physical properties.
Now, magnesium (Mg) has 2 electrons in its outermost (3s) atomic shell. The other elements which have 2 electrons in their outermost atomic shell are beryllium (Be) and calcium (Ca).
So, the elements having atomic number 4 is beryllium (Be) and atomic number 20 is calcium (Ca) and have chemical properties resembling magnesium (Mg).

Note:
It should be noted that the elements beryllium (Be), magnesium (Mg), and calcium (Ca) belong to group 2 of the periodic table and are also known as alkaline earth metals. At standard pressure and temperature, these metals are somewhat reactive and are all silvery-white and shiny.
They have completely filled the outermost s-orbital. They form cations having a +2 charge and an +2-oxidation state.